
let _Vue = null
class VueRouter {
    static install(Vue){
        //1 判断当前插件是否被安装
        if(VueRouter.install.installed){
            return;
        }
        VueRouter.install.installed = true
        //2 把Vue的构造函数记录在全局
        _Vue = Vue
        //3 把创建Vue的实例传入的 router 对象注入到 Vue 实例
        // _Vue.prototype.$router = this.$options.router
        _Vue.mixin({
            beforeCreate(){
                if(this.$options.router){
                    _Vue.prototype.$router = this.$options.router
                }
               
            }
        })
    }
    constructor(options){

        this.options = Object.assign({}, {mode: 'hash'}, options)
        this.routeMap = {}
        // observable
        this.data = _Vue.observable({
            current: "/"
        })
        this.init()

    }
    init(){
        this.createRouteMap()
        this.initComponent(_Vue)
        this.initEvent()
    }
    createRouteMap(){
        //遍历所有的路由规则 把路由规则解析成键值对的形式存储到 routeMap 中
        this.options.routes.forEach(route => {
            this.routeMap[route.path] = route.component
        });
    }
    initComponent(Vue){
        let that = this
        Vue.component("router-link",{
            props:{
                to:String
            },
            render(h){
                return h("a",{
                    attrs:{
                        href:this.to
                    },
                    on:{
                        click:this.clickhander
                    }
                },[this.$slots.default])
            },
            methods:{
                clickhander(e){
                    that.options.mode === "hash"? this.hashHander(e) : this.historyHander(e)
                },

                // hash：4、自定义跳转方法
                hashHander(e){
                    location.href = `${location.origin}${location.pathname}#${this.to}`
                    e.preventDefault()
                },
                
                // history：3、自定义跳转方法
                historyHander(e){
                    history.pushState({},"",this.to)
                    this.$router.data.current=this.to
                    e.preventDefault()
                }

            }
            // template:"<a :href='to'><slot></slot><>"
        })
        const self = this
        Vue.component("router-view",{
            render(h){
                // self.data.current
                const cm=self.routeMap[self.data.current]
                return h(cm)
            }
        })
        
    }
    initEvent(){
        if(this.options.mode === "history")
            // history：2、浏览器前进后退按钮监听popstate事件
            window.addEventListener("popstate", () => {
                this.data.current = window.location.pathname
            })
        else
            // hash：2、浏览器地址栏修改hash值
            // hash：3、浏览器前进后退按钮、或者调用浏览器API
            window.addEventListener("hashchange", () => {
                this.data.current = window.location.hash.replace(/\#/g,'')
            })

        window.addEventListener("load", () => {
            if(this.options.mode === "history")
                // history：1、浏览器首次输入url或者修改url，通过 pathname 获取当前路由地址
                this.data.current = window.location.pathname
            else
                // hash: 1、浏览器首次输入url
                this.data.current = window.location.hash.replace(/\#/g,'')
        })
    }
}

export default VueRouter